Alternating-current printing-telegraph system



Sept. 14 1926. 1,599,445

E. F. WATSON ALTERNATING CURRENT PRINTING TELEGRAPH SYSTEM Filed sept. 17, 1924 2 Sheets-Sheet 1 19 fiz f5 jllzfl in inter [019134591- I I I I v J 2 72 Jelectz' /vl 'wm 2 12, 5 NA 4 Q? .gl b e F l /7[ Jelectz'l/z Mayne;

i 5 INVENTOR EFT M55010 ATTORNEY I At eachlocal station-a selective apparatus Patented Sept-'14, 1926'.

UNITED STATES PATENT OFFICE."

EDWARD r. WATSON, oF L AnoHmoNr, NEW YORK, ASSIGNOR To AMERICANTELE- PHONE ANnrELEonArn COMPANY, A oonrona'rron on NEW YORK.

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Application filed September This invention relates to printing tele- .graph systems, and more particularly to printing telegraph systems in which alternating currents or so-called carrier currents are used forthe transmission of signals. The present application is a continuation of the common subject matter of my application, Serial No. 379,887, filed May 8, 1920 One of-ihe Objects of the invention is to" provide a printing telegraph system in which the elements of a code combination are formed by carrier currents of' diiferent frequencies, these frequencies being supplied ,to the circuit at a central point and trans-' -mitted to. the different local stations associated with the circuit in a manner analogous to the central battery supply of current to the sub-station in a telephone system. By

,snpplycurrent may be utilized for a number of difierent circuits, and signals may be transmitted betweenstations in each circuit without transmitting the signals to the other circuits supplied with current from the same source.

- Another object of the invention is to pro-- vide a printing telegraph system-in which the selective apparatus responsive to the code combination at each station shall be as simpleas possible. 1 Still another object of the invention is to provide a. printing telegraph system in :which the use of distributors at both the transmitting and receiving stations is eliminated. j v

Other and further objects of the invention may be realized in an arrangement in. which all of the local stations are included 'in', a closed loop supplied with "currents of different frequencies at some common point.

consists of a number ottuned circu ts corresponding to the number of difl'erent selecting impulses required with anadd-itional tuned circuit in certain'instances to control the printing operation. yIn series with each of these ,tuned circuits is an alternating current relay. The selective operation of these relays in response to the transmission-of d'if-' ferent combinations of frequencies operates the printer. For sending purposes a trans- :mitting contact is included in each tuned. circuit, and'by opening or closing difierent combinations of contacts, thereby opening and closing difi'erent tunedcircuits at the 17, 1924. Serial- No. 738,228.

local station. the impedance for different frequencies is varied, so that the correspondng receiving relays at-all of the stations will respond. By connecting a number of suchloops in parallel to common busbars supplied with current from the same alternating current sources, signaling may take place in each loop without affecting the other loops, provided there is substantially no impedance in the circuit leading from thetbusbars to the source or sources of curren The invention'may be more fully understood from the following detailed descrip-, tion when read in. connection with the ac companying drawing, Figure 1 of which represents in schematic form the circuit arrangement of the proposed system; Figure 2 of whlch is a-detail of the circuit arrangement of the selective relays, Figure 3 of which is an alternative form of sub-station, circuit, and Figure 4-of which illustrates in somewhat more detail how-a pluralit of independent loops may be connected to husbars to which a common source is applied.

Referring to the drawing, L designates a transmission circuit in the form of a closed loop, including sub-station apparatus at substation, A, B and C. ,In the system illustrated, a code analogous-to the .Baudot code is employed, and in order to transmit this code, the loop circuit is supplied at a central station D with six diflerent frequencies, five of which corres 0nd to different elements of the Baudot 00 e, and the sixth of which is to institute the printing operation in a Well known manner. These frequencies may be applied to other loops in parallelwith the loop illustrated as indicated by the multiple connections at the central oifice D.

The apparatus at each sub-station is identical, and as indicated at station B, consists of six tuned circuits, 1, 2, 3. 4, 5 and 6,

closed, but to be open during the printing operation. The circuits controlled by the; five selecting relays and the sixth pulse relay aretindicated in more detail in Figure 2. Thelfive selecting relays, it will be noted, are each arranged to close a circuit through one selecting magnet of the printer When the selecting relay is de-energized. The selecting magnets and other apparatus of the printer are well known in the art, and need not be illustrated or describedin detail, as they form no part of the present invention. The sixth pulse relay R is arranged so that whenit is de-energized a circuit is closed over a sixth pulse conductor to set the printer in operation in a Well known manner to print the combination set up on the selecting magnets.

The operation is as follows:- Normally, each of the six frequencies supplied at the central oflice flows over the circuit and at each sub-station finds a path of low impedance circuit. If" now, one of the stations, say, station B, is transmitting, certain of vthe transmitting contacts will be open, while others will be closed in response to the actuation of a key. The transmitting contact T is opened each time a key is actuated. Assuming that transmitting contacts T T and T,, are 0 en in addition to the contact T at station E, the frequencies f f f and f will nowflow over the line L through an impedance very much greater than thatex isting before, since the tuned circuits atsta tion B which remain closed have a very large impedance for frequencies other than thosefrequencies to which they are tuned, conse quently relays R ergized at station B'due to the opening of their circuits, and the corresponding relays at the other stations are also de-energized because of the increased impedance for currents of the frequencies which normally flow through said relays. The circuits of the selecting. magnets corresponding to 'the first, third and fifth selecting relays are operated at each station to set up the proper code combination on the printer and the corresponding character is rinted by the transmission of the'sixth pu se to the printer over the back contact of the sixth relay.

As the contact 10 in the'sixth selective circuit is held open during the operation of printing any given character, the sixth selective circuit cannot be closed until the last character has been completely printed, and

,the printing of another character due to the setting up of a new combination on the .selecting relays cannot take place until-the combination previously set up has been printed by all of the printers on the circuit. It will be obvious that loops other than .theone described, connected to the. common sources and provided with signaling equip ment similar to that illustrated. will not .be affected by the. signals transmitted in the loop above'described. This is for the ma through the corresponding tuned 11 ,3 and R are de-envoltage drop across the common busbars to which the loops are connected in parallel and upon the impedance of the loop itself common source and is not determ ned by the impedances of any'or all of the loops. It 4 is assumed, of course, that the connections from the busbars to the source have. sub.- 'stantially no impedance. in order that the condition just described may obtain.

A modification of the system is shown in Fig. 3. In this modification only five tuned circuits are employed, and the. printing operation is started Whenever any one of these tuned circuits is opened. This, of course, prevents the use of a code combination in which all fire selecting relays are held energized so that no printing magnets are actuated. In this caserthere would be nothing to start the printing operation. The system, however,has' the obvious advantage that it eliminates one of the tuned circuits or channels required in the system previously described in order to start the printing operation for a combination in which the five character-determining relays are unreleased. The operation of the arrangement shown 1n Fig.3 is the same with respect to the act-uation of; the selecting magnets of the'printeras that illustrated in Figs. 1 and 2, and need not be further described. Upon the release ofany selecting relay in response to the transmission of a signal, as, for instance, the selecting relay R,, a circuit is completed from ground to the winding of the corresponding selecting magnet, such as M over the back contact of the selecting relay and through the winding of relay 11 to battery; Relay 11 at its front contact completes a circuit through the left-hand winding of relay 12 and over back contact of relay13 tobattery. Relay 12 at its right-hand front contact completes a locking, circuit through its right-hand Winding and over the clear-out contact 14 to ground. The sixth pulse to operate the printer is also transmitted at the same time. Relay 12 also completes a circuit from battery over itslefthand front contact and through the winding of relay 13 to ground. Relay 13 opens the initial energizing circuit of the relay 12. Relay 13 at its right-hand front contact completes locking circuit through its own winding, and is consequently maintained energized untilall of the selecting contacts T to' T inclusive have again been closed upon "restoring the transmitting key to normal. When this occurs, relay 11 is de-energized. and at its back contact short-circuits the winding of relay 13. Relay 13 is accordingl'yreleased and if the printing operation has been completed the three relays 70 at that frequency. The voltage drop across T the busbars is equal to the voltage of the 11, 12 and 13 are again in normal condition ready to function in printing'the next character. In case the transmitting contacts are held operated andthe relay 11 remains operated after the printing operation is completed relay 13 will remain operated, and relay 12 will be releasedrby the opening of its lock relation between a plurality of independent signaling loops supplied by a common source at D and how difierent signaling stations may be interchangeably connected in difierent loops so that the various stations may intercommunieate in separate groups. The various frequencies f, to f, are supplied by suitable sources (not shown) at station D,

the voltage from the sources being applied .to the busbars 20. Across these busbars are connected. a plurality of groups of jacks, such as groups J J,, J and J J and J,. The individual jacksof each group have their contacts arranged in series with respectto each other, but the groups themselves are connected in parallel. In the idle condition of each group of jacks, one of the jacks, as, for example, J is open-circuited to prevent short-cireuiting the busbars.

A plurality of locall'ines or loops, such as L L and L each provided with substation equipment similar to that of Fig. 1,

as indicated at A, B and C, terminate in plugs P P and P By inserting these plugs in the jacks of groups such as J J and J the three signaling stations, such as A, B and C, will be connected in series across the busbars. The circuit extends from the right-handv busbar, overthe tip conductors of jack J and plug P over the upper conductor of the loop;,L.', through the substation apparatus at A, over the ring conductor of the loop' L over the ring contacts of the plug P and the jack J over thetip conductors of the jack J and the plug "P over the tip conductor of the loop L through the substation apparatus at B over the ring conductor of the loop L over the ring contacts of the plug'P and the jack J over the tip conductors of the jack J 3 and the plug P over the tip conductor of the loop L "through the substation apparatus at G, and then back over the ring conductor of the loop L and the ring contacts of the plug P and the jack J 3 to the left-hand busbar. Signals may be transmitted over the above circuit between the stations A, B and C in.

the manner described in connection with Fig.

in many other organizations widelydifte Other substation loops may be plugged into other groupsof jacks for independent intercommunication; for example, the loops L and L terminating in substation ap paratus E and. F, are connected in series by insoi :ing the plugs P and P in the jacks J and J of the group J J and J,. The substation apparatus E and-F is now ar-' ranged in series in an independent loop,

the loop, however, being in parallel with 7-5 the loop including the substations A, B and C. Other loops and plugs are provided as indicated so that 'the various substations may be connected in groups, whereby the stations of each group may intercommunicate 0 independently of the stations of other groups. The number of jacks in each group may be any number desired, three being shown in the drawing forpurposes of illustration.

Assuming'that there. is substantially no impedance in the connections from the busbarS to the sources, the voltage drop across the busbars at any frequency will be equal to the voltage generated by. the generator of that frequency. The current flowing in any loop formed by inserting the plugs connected to individual stations into any group of jacks depends upon the series impedance of the loop, at a given frequency and the voltage drop across the busbars at that frequency. Since the voltage drop across the busbars is not appreciably'afiectedby what hap ens in any other loop connectedacross the usbars, a change in the impedance of any other loop at a given frequency does not ,afiect the current flowing at that he 'quency in the given loop. Therefore, signals may be transmitted between the Stations in the loop bv interrupting combinationsfof selecting branches at the substations. This changes the impedance ot-the given loop at the several frequencies involved but does not affect the current flowin any'of the other loops at those frequenno cies. Therefore, the signals may be transmitted in any loop without aitecting substations in'other loops.

It will be obvious that the general principles herein disclosed may be embodied: D

ent from those illustrated without departing from thespirit or" the invention, as defined in the following claims.

What is claimed is i 1. In a printing telegraph system, a transmission circuit, means for impressing a plurality of frequencies upon said circuit, a substation comprising a plurality of paths arranged in parallel with respect to each 125 otherand each being 1n series with said transmission circuit, means to render each path selective to a different, one of said frequencies, a transmitting element and a receiving element in each path, said elerality of frequencies upon said circuit, a plurality of subscribersstations associated I circuit, means to render each of the paths with said circuit, each subscribers station including a plurality of paths arranged in parallel to each other and each path being in series with respect to said transmission of each subscribers station selective to a "different one of said frequencies, transmitting meansand receiving relaysincluded in each selective circuit, said transmitting means and receiving relays being in series with each other and serially included in the selective circuit, and a printing apparatus jointly controlled by said relays.

3. In a printing, telegraph system, a transmission circuit, means for-impressing a plurality of frequencies thereon, a plu rality of subscribers stations, each subscribers, station including a plurality of paths, one corresponding to each frequency, said paths being arranged in parallel ith respect to each other but each path being arranged in series with res ect to said transmission circuit, means for rendering the paths of each subscribers station selective to a different one of said frequencies, re-

ceiving relays in each of said selective paths, the receiving relays of a given substation being arranged to jointly control printing apparatus, transmitting means in each selective path, the transmitting means of the selective paths of a given subscribers station being arranged to selectively control said selective paths to cause the actuation of corresponding relays at each of said stations, and the transmitting means and, re-

ceiving relays of each path being arranged in series with each other and serially included in the path.

4. In a printing telegraph system, a transmission circuit, means to impress a plurality of frequencies thereon, one corresponding to each element of a printing telegraph code, a plurality of subscribers stations associated with said circuit, each subscribers station including a plurality of selective paths, one corresponding to each frequency, said selective paths being arranged in parallel with respect to each other but being serially included in said transmissioncircuit, a receiving'relay in each of said selective paths, means whereby the relays in the paths of each subscribers station jointly control printing apparatus, and transmitting devices in each path, said transmitting devices being arranged so that the transmit ting devices of the paths of a given' subscribers station selectively control said selective paths to cause the actuation of corresponding relays at each substation, the transmitting device and receiving relay of each path being arranged in series with each other and in series with the path.

5. In a printing telegraph system, a transmission circuit comprising a closed loop, means for impressing a plurality of frequencies upon said loop, each of said he quencies corresponding to one of the elements of a Baudot code, a plurality of subscribers stations each including a'plurality of paths, one corresponding to each frequency, the said paths of each substationbein' arranged in parallel with respect to eac other andeach path being in series with respect to the loop, means to render each path of each. substation selective to a different frequency, transmitting keys in each path means for impressing a plurality of frequen'cies upon said loop, each frequency corresponding to one of the elements of the Baudot code, a plurality of subscribers stations having transmitting and receiving apparatus serlally included in said loop, each transmitting and receiving apparatus com.- prising a plurality of selective circuits each corresponding to one of the frequencies impressed upon the loop, selective relays in each selective circuit for jointly controlling the printing operation and'normally closed transmitting contacts, one in each selective circuit, the selective operation of said con tacts opening the circuits of selective relays in certain of said selective circuits at the station where the transmitter is operated, thereby causing the selective relays to select thechgracter to be printed, the opening of said selective circuits by the actuated contacts also increasing the impedance of the transmission circuit for the corresponding frequenciesso that the corresponding relays in corresponding selective circuits at other the transmission of said frequencies over.

said circuit without affecting the transmission of said frequencies over other transmission circuits, and means individual to each circuit selective to the several frequencies.

8. In a signaling system a plurality of transmission circuits, means common to said circuits for impressing each of a plurality of frequencies upon all of said circuits, means individual to each circuit for individually controlling the transmission of each of said frequencies over said circuit without affecting the transmission of said frequencics over other transmission circuits, and

means individual to each of said circuits individually selective to each of said fre qucncies.

9. In a printing telegraph system a plurality of transmission circuits, means common to said circuits for impressing a plurality of frequencies upon each of said circuits, substations associated with each circuit, one substation of each circuit including a transmitting apparatus for controlling the transmission of each of said frequencies without affecting the other transmission circuits, and another substation of each circuit including means selective to each of said frequen-- substations for each circuit including a receiving apparatus comprising a plurality of selective circuits, each selective to a different one of said frequencies, and means joint- 1y controlled by said selective circuits of each transmission circuit for controlling a printing apparatus.

11. In a signaling system, means for generating alternating voltages of a plurality of frequencies, a plurality of signaling loops connected in parallel to the common voltage terminals of said generating means, a plurality'of signaling stations in each loop, means at each station for controlling the transmission in the loop of current of the frequencies generated by saidgenerating means without affecting the current of such frequencies flowing in the other loops, and means at each signaling station selective of the several frequencies.

12. In a signaling system, means for gencrating alternating voltages of a plurality of frequencies, a plurality of independent loops connected in parallel to the common voltage terminals of said generating means, a transmitting station and a receiving station serially connected in each loop, means at each receiving station responsive to changes in the impedance of its loop at the several frequencies, and means at each transmitting station to change the impedance of the loop in which it is located at any of the generated frequencies without affecting the current flow in the other loops at said frequencies, whereby the receiving station in any loop will respond to the transmitting station in that loop but will not respond to transmitting stations in other loops.

13. In a signaling system, means for generating alternating voltages of a plurality of frequencies, a plurality of loops connected in parallel to the common voltage terminals of said generating means, a transmitting station and a receiving station in each loop, each receiving station comprising a plurality of circuits individually selective of the several generated frequencies, means in each of said circuits responsive to a change in the impedance of the loop at the corresponding frequency, each transmitting station comprising means for individually changing the impedance of the loop at any frequency without changing the current flow in any other loop at that frequency, whereby signals may be transmitted between the stations in any loop Without transmitting signals to stations of other loops;

In testimony whereof, I have signed my name to this specification this 15th day of September, 1924.

EDWARD F. WATSON. 

